Modern plate mills produce plates that, when wound up, are referred to as coils. In order to monitor the quality of the steel, samples are usually taken from the leading or the trailing end of the strip. Automated inspection systems and sampling stations are available for this purpose up to a medium thickness range of about 12 mm. Samples in the upper thickness range of >12 mm (up to about 25 mm) are frequently taken with the help of simple roller support troughs in which the coil can be rotated. The sample is then obtained by manual flame cutting. However, this method has the disadvantage that it is dangerous for the operator, as, because of their stiffness and elasticity, the ends of the strip can whip around, the coil can roll out of the roller support trough, and the productivity (namely the number of samples per unit time) of such a simple station is low due to the large amount of time involved.
Different qualities of steel, which can be roughly divided into three basic groups, are processed in a modern rolling mill. First, there are the normal, usually hot-coiled structural steels that are plastically deformed when coiled up. In practice, a free final turn of the strip rests on the coil. When, for example, the end of the strip is to be fed into a shear, the end of the strip must be peeled from the coil. Second, there are high-strength fine-grained structural steels that are coiled after having been thermomechanically rolled in the medium temperature range. Because of the high strength of the steel, the plates are only partially plastically deformed. A free final turn of the strip has a larger diameter and stands somewhat away from the coil. Third, the steel qualities used are ultra high-strength steels that are hardened and tempered in the rolling process and have extremely high strength. These materials with maximum strip thicknesses of only approximately 15 mm are only downstream stretched elastically when coiled up. After releasing the coil strapping, a free final turn of the strip assumes its fully extended straight form from the rolling mill once more.
FIG. 1 shows the behavior of the three different steel qualities mentioned above in a typical roller support trough. The coil is supported on two trough rollers 2, 3 and the coil strapping has already been released. While the free end of the normal structural steel, shown at [1], rests close to the outer surface of the coil, the partially plastically wound high-strength steels, shown at [2], spring open at their free end from the region on the right of the right-hand trough roller 3 and accordingly detach from the outer surface of the coil 1. Finally, because of its purely elastic winding in the coil, the ultra high-strength steel, shown at [3], springs back completely into its original shape when the coil strapping is released.
Sampling stations that feed the strip into the separator, for example a shear or plasma burner, are therefore already known in practice. Here, strip of types [1] and [2] undergoes a plastic deformation in which the uncoiled strip end is badly bent and, as a result of this bending moment, the coil can be raised so that a snubber roll may be necessary. In addition, when winding up, it is no longer possible to bend the end of the strip completely against the coil. Such a system according to the prior art is shown in FIG. 2. The free end of the metal strip 4 that has been wound to form a coil 1 is peeled from the outside of the coil 1 by a strip channel 5 and then forcibly fed to a shear 6.
With this method of working, correspondingly large forces, which have to be absorbed by the structure, are produced as a result of the high force. These forces also involve a high level of deformation work and therefore very high drive power in the roller support trough. The coil must also be stabilized by additional other rollers and/or needs large other roll forces in order to be able to transfer the uncoiling torque into the coil. Finally, the strip is pushed/rubbed against force-inducing surfaces and, in combination with the large supporting forces, this damages the strip surfaces.
Further designs are known from practice, for example supporting the coil on a mandrel in combination with different coil opening systems that, however, are all jointly characterized in that the strip is fed into the separating system with a large curvature and therefore under the above-mentioned disadvantages.
Newer developments in this field are shown in FIGS. 3 and 4. After the coil has been transported into the roller support trough comprising rollers 2, 3, the coil strapping is usually removed by a chisel at the end of the swivel table. Immediately after the coil strapping is removed, the strip then springs open as described above to an extent that depends both on the rolling process and on the rolled steel quality. By rotating the coil 1 by turning the trough rollers 2, 3, the strip is pushed into the shear 6 and the end of the strip is cut off for sampling. The leading end 4 of the strip is detached from the outside of the coil 1 by a guide device and fed toward the shear 6. As the required effect must be developed continuously for different coil diameters, the guide device 5 can preferably be pivoted into the intermediate space between the leading strip end 4 and the outer surface of the coil 1 (FIG. 3) or moved in a straight line (FIG. 4).